Stopping down w/ polarizing filter.
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“Note that because a polarizing filter cuts the light down by 2 stops, I had to increase my shutter speed by 2 stops…”
I don’t know if he’s using a hand-held meter there or something but while a polarizer will eat up around two stops of light your camera will be metering the light after it’s passed through the filter so you don’t really need to think about it like that.
Sometimes a little compensation is desired because images can look dark when the effect is at it’s strongest but it’s not going to be on the level of two stops.
I lent my copy of the book to someone Dusty and I really like to know the chapter thats in and the full the context within which its given.
As it makes no sense what so ever.
Dusty did you mistype it?
A CP will reduce the light hittng your sensor by about 2 stops.
If you meter the scene first ( no CP) or if your using an incident meter (which he does go into in 1 chapter) the meter reading will determine a proper exposure sans CP in either caseThen you add the CP, which reduces the light by 2 stop. Your now underexposing by 2 stops. If your further increase the shutter speed by 2 stops, your underexposing by 4 stops.
As Carter said if you meter the scene with your body with the CP in place, the proper exposure is still the correct expouse. Take the shot, check your histo and if its too dark increase exposure by a 1/3 or 2/3 or by however much clearance is between the last pixels on the histo and the far right (255)
You can generally tell by looking at the Histogram if you have room to increase exposre by a third, half, full stop or more just by looking at the histo and the gap between 255 (blown pixels) and the far rigt edge of the luminoisity graph
***************As for CPs sometimes I play with them whenever/whatever but as a general rule I’ll add them when
Theres alot of glare, water, Chrome, etc
When I want to slow my shutter speeds further than a proper exposure for a given scene will alow w/o overexposing the shot.
Classic example is moving water…gentle waves, streams, fountains,waterfalls.
Without the CP your shutter speed will be say X
With the CPI leave mine on whenever I can get away with it
Carter,
How do you determine this?John,
The chapter is titled Special Techniques and Filters. It is located on page 146.He is discussing the effects of glare, and how the use of a pol. filter has brought out more color in a waterfall. Both pics were shot in the following:
24mm lens
f/22
one for 1/4 sec. w/o pol. filter
other for 1 sec. w/ pol filter.So, should I not worry about stopping down 2 w/ pol. filter?
DustySorry John,
I forgot to add that he is shooting a waterfall surrounded by greenery with no visible sky.
D.f/22
one for 1/4 sec. w/o pol. filter
other for 1 sec. w/ pol filter.1 second is what his meter started reading as a correct exposure after he put the filter on.
ok.
On the surface if you take the quote.
“Note that because a polarizing filter cuts the light down by 2 stops, I had to increase my shutter speed by 2 stops…
Its dead wrong.
A proper “exposure” that then adds a CP (-2 stops) and then increases SS by yet another 2 stops will be underexposed by 4 stops for a proper exposure, relative to a reading taken without the CPis etiher a typo in the book itself or theres something missing
*****************F22 for 1/4 second ( no CP) = a proper exposure.
F22 for 1 second with CP…By adding the CP if you want the same proper exposure he’s decreased the shutter speed…in other words left the shutter open longer. You have to. The CP reduces the amount of light hitting the sensor, so you need to increase your exposure accordingly..You an do that by decreasin SS by 2 stops or by decreasing SS 1 stop and lowering ISO 1 stop…That last just for example
I’m going from memory and its been a few years so I may be mistaken. Take what I’m about to say with that in mind.
The book is largely about 2 things.
1) Getting people to understand the exposure triangle ( F/stop,ISO,SS) and how by changing any of the 3 soley or in combination you can still arrive at the same proper exposure
2) Metering scenes and how often you want to ignore what the camera is telling you is a proper exposure.
With incident and spot metering, you meter “something” set your values to render a proper exposure. Recompose and ignore what the cameras light meter is now telling you. Earlier in the book you would have read about Brothers Blue Sky and Green Fields?
If I remember correctly when discussing waterfalls., you set your exposure values for the greens left and right of he waterfall, not the waterfall itself. So in M mode meter off the Greens present, set your values (iso,fstop,ss) and recompose. Or Meter off the water falls (whites) and adjust accordingly for the greens…
The simplier thing todo is meter with the CP on, set your values and your good to go
The exposure thing is covered above, but I will add a little about when & where to filter.
Polarizers can be over-used, sometimes the reflections make the shot IMO and to blanket wipe them means you might be missing out.
I only use them (in fishing stuff) for big wide angle shots with lots of sky and to get longer exposures for flowing water shots.
All that said, you shouldn’t ever be without one for fishing shots..
Exposure wise, my cameras (DsIII’s) like about +1/2 a stop exposure compensation when shooting wides with a polarizer in our hard light.
(center weighted metering)
It stops the shadows from getting to dense and leaves me a little room to adjust in post if needed.Last thing, polarizers vary in quality greatly, I’ve found the Hoya’s I’ve been using are crap compared to some new B&W or Schnieder’s I’ve now got.
They cost HEAPS more, but are more even, have better color and don’t fall apart like the Hoya’s..www.dsaphoto.com
A picture is thousand words that takes less than a second while a thousand words is a picture that takes a month.
Thank you for the help guys; your explanations helped dramatically. The author may have simply been operating on some basic assumptions, i.e. the reader would have some inkling! Or maybe I just failed to apply elements he had previously discussed when I got to that quote. That’s why I’m re-reading the book.
After reading that section of the book, I looked back at some images and noticed the sky got deeper and deeper blue toward the top of the image. Only the tops were effected this way. Does this mean I did not have the filter in the correct position? I am guessing this is why the filter rotates.
Dusty
You need to have the filter rotated properly to get the full effect – it’s fairly easy to see when you have it right..
The sky get’s darker and you can see the reflections come off..
www.dsaphoto.com
A picture is thousand words that takes less than a second while a thousand words is a picture that takes a month.
Sorry Dusty. What David said.
Most CPs also come with a hash mark or triangle on the rim to aid you orientating it. Basicaly point the hash mark at the sun if you don’t have time to look through the viewfinder as you spin the CP and judge how much or how little effect you want. A CP will be at its strongest when its perpinduclar to the sun.
Minimising, or removing that effect when part of the sky is heavily influenced is something I haven’t quite figured out. Hard to see with the naked eye on scene, but is obvious once the image is on your pc.
In the above the original is even more pronounced at the top left and trailing off to the right, lower right. I lessened it a bit with the aid of a Grad ND filter in post.
Don’t wear polarised sun glasses when looking through the viewfinder and trying to adjust the CP
Don’t wear polarised sun glasses when looking through the viewfinder and trying to adjust the CP
I never would have thought about this, but now that you mention it, it makes perfect sense.
When I go out this weekend, I will apply all that y’all have said. I am starting to understand my camera more and what creates correct exposures, thanks to all of you and and a few websites. Hopefully, by the end of the weekend, I will have some images to show, and I/we will be able to see where the reading and advice paid off, just as long as I follow the instruction.
I am taking my bro-in-law fishing, and he has never held a flyrod. I could be digging flies out of my or his skin, which I think would make for some interesting images if I manage to get the correct exposure.
Thanks guys,
DustyI still think some of you guys need to write a book!
I took all of your suggestions to heed and went out Sat. morning, but the light was still a little harsh-probably should have set out earlier. But here is what I feel is the best exposure of the 75 I took:
While not trying new stuff with the camera, I handed it over to my buddy and managed to bring a couple to hand:
Dusty
I played with the image a bit, and after deciding the out-of-focus log took up too much of the frame, I did a small crop, rotation, and a small amount of added color.
DustyDusty, I like the second image better. I think you are right that the log took up too much room and kind of drew your eye away from the angler. Looks like some fun carping!
Lake Ray Roberts, about an hour north of Dallas. You’re right-there are some good LMB in there, but if you are going to travel for LMB, I suggest you head to Lake Fork.
DustyYeah Dusty im with Scott and John in that I like the second one more. Also John you might want to check out O.H. Ivy if you want some big LMB, but its the wrong time of year. So keep that in mind for like next March.
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